1. Field of the Invention
The present invention relates to an image forming method and an image forming apparatus, and more particularly, to technology for insolubilizing the coloring material contained in an object liquid, such as ink, by means of a prescribed treatment liquid.
2. Description of the Related Art
In recent years, inkjet recording apparatuses (inkjet printers) have become widespread as image forming apparatuses for printing images. An inkjet recording apparatus prints a desired image by ejecting ink droplets from an inkjet recording head, onto a recording medium, such as recording paper, while moving the recording medium and the inkjet recording head relatively with respect to each other.
In an inkjet recording apparatus, in order to avoid bleeding and obtain a clean image, desirably, the coloring material contained in the ink is fixed rapidly onto the recording medium. In view of these circumstances, various technologies have been proposed for rapidly fixing the coloring material onto the recording medium, by insolubilizing the coloring material in ink deposited onto the recording medium by means of a prescribed treatment liquid.
Japanese Patent Application Publication No. 2005-119115 discloses an inkjet recording apparatus in which the deposition volume of a reactive liquid per unit surface area of a recording medium is varied in accordance with the differential between the landing times of the reactive liquid and the ink on the recording medium, and the reactive volume of the reactive liquid and the reactive volume of the colored ink are set to be approximately the same. Japanese Patent Application Publication No. 8-72229 discloses an inkjet recording apparatus in which a low-resolution mode using ink only, and a high-resolution mode using ink and treatment liquid are used.
In an image forming apparatus such as an inkjet recording apparatus, desirably, the diameter of the dots formed on the recording medium by the ink droplets is adjusted in accordance with the desired density. For example, in a high-density region, in order to form an image of high density, it is desirable to prevent the appearance of white background color by increasing the dot diameter. On the other hand, in a low-density region, it is desirable to improve the image granularity by making the dot diameter sufficiently small.
However, in the inkjet recording apparatus according to Japanese Patent Application Publication No. 2005-119115, since the reactive volume of the reaction liquid and the reactive volume of the colored ink are approximately the same, then the diameter of the ink dots is virtually uniform. Consequently, it is difficult to actively change the ink dot diameter. If the dot diameter is made relatively small, for example, then in the high-density region, it is difficult to make mutually adjacent ink dots contact each other, thus making white background color liable to appear. On the other hand, if the ink dot diameter is made relatively large, then it is difficult to ensure good image granularity. In this way, in the inkjet recording apparatus described in Japanese Patent Application Publication No. 2005-119115, it is difficult to satisfy both “improvement in the image granularity in the low-density region” and “prevention of the appearance of white background color in the high-density region”, in an efficient manner.
Furthermore, the inkjet recording apparatus according to Japanese Patent Application Publication No. 8-72229 is disadvantageous in terms of the “improving the granularity of the image in the low-density region”, since the treatment liquid is not used in low-resolution mode, and therefore, it is difficult to make the dot diameter sufficiently small. On the other hand, in the high-resolution mode, a fixed volume of the treatment liquid is used and the dot diameter may be made too small, which is disadvantageous in terms of the “preventing the occurrence of background white color in the high-density region”.
Therefore, the technology for achieving both the “improvement of image granularity in the low-density region” and the “preventing the occurrence of background white color in the high-density region”, in an efficient manner, have been expected.